1. Field of the Invention
This invention relates to remotely controllable vehicle systems such as security and/or keyless entry systems, employing remote, wireless transmitters for its operation and control. More particularly, this invention discloses a novel way to program the controller of the security system to recognize a particular remote transmitter(s) as an authorized transmitter(s) in an environment subject to EMF and RF noise.
2. Description of Prior Art
Remotely controllable vehicle security systems have found a profound place in today's society. Consumers purchase these systems as a theft deterrent, as a personal shield against crime and as a convenience item for keyless entry into their vehicles. As these systems evolve, manufacturers have recognized market demand for remote transmitters capable of arming and disarming vehicle security systems and/or locking and unlocking vehicle doors. Today, virtually all such systems operate under the control of remote transmitters generating a discrete signal and controlling systems specifically tuned to respond to that signal.
The more sophisticated remote transmitters encode a specific code word into the high frequency wireless signal. The system receives the signal and decodes it into the original code word. Thereafter, it compares the received identification word therein to a set of authorized identification words stored in a memory. If the identification words match the authorized identification words, the system proceeds to respond to the command transmitted by the remote transmitter.
Originally, these systems were preset or hard-wired to respond to a specific authorized identification word embedded within or assigned to the system. If two or more users wanted to operate the same system, it required that each user have a transmitter programmed or wired to the specific authorized identification word which the system would recognize. The market did not respond to this requirement positively. Transmitters were lost and difficult to replace. Additionally if multiple authorized users were using multiple cars equipped with these systems, these users were required to carry with them multiple remote transmitters, one for each vehicle.
To overcome this problem the industry provided a learn mode wherein the system enters a learn mode/routine and accepts the transmission of a nearby remote transmitter having an identification word therein as the authorized identification word to operate it. This process is described in the U.S. Pat. No. 5,049,867. This patent discloses a learn mode/routine for a security system where the controller is set to a learn mode/routine for a period of time, such as fifteen (15) seconds, by turning on the ignition and opening a door. The controller of that system recognizes that it is commanded to its learn mode/routine by sensing the ignition on condition and the door open condition. The system must then receive a predetermined number of identical identification words during a continuous serial transmission from a transmitter having a recognizable identification word. Thereafter, this system will register the identification word sent to it as an authorized identification word for operation of the system and stores it for future use.
The system described in the aforementioned patent has drawbacks. It requires the security system to be hardwired to a number of sensors which provide the controller with the status of conditions necessary to activate the learn mode/routine. Also, these systems are generally more expensive than the two wire systems which only have power and ground (common) inputs with an integral siren. These two wire systems would be incapable of learn mode as described in this patent.
To overcome the aforementioned problem with two wire systems, the industry used the transition from power off to power on to indicate and activate the learn mode/routine. Thereafter, any signal received by the system is registered as the authorized identification word for its operation.
Present day systems are subject to false programming in an environment where there is EMF or RF radiation or interference.
This problem is commonplace about two way radios, industrial motors, television, radio antennas and the like. This problem is also apparent in the store locations where these devices are installed because a number of installers may be programming transmitters or test operating systems at the same time. Therefore, the system being programmed may learn stray signals and/or learn a remote transmitter which is not assigned to the intended vehicle.
Therefore, there remains a need for a remotely controllable vehicle system capable of being programmed for operation with a specific remote transmitter or transmitters, each transmitter having a unique identification word therefor and capable of eliminating, during its learn mode/routine, the input of stray signals and signals transmitted by other undesired remote transmitters.